As a solid polymer electrolyte which uses a polymer having an acrylic ester derivative, which has a polyalkylene oxide chain at the ester moiety thereof, as the repeating unit, a solid polymer electrolyte, for example, which is formed from a matrix component of a crosslinked polymer (A) and electrolyte salt (B) and is produced by the polymerization reaction of the matrix component (A) and which is characterized by containing at least a urethane (meth)acrylate-based compound (A1) and polymerizable monomer (A2) represented by the following formula (1) is conventionally known (refer to Patent document 1).

In the formula, R101 represents hydrogen or C1-4 alkyl; R102 represents hydrogen, C1-4 alkyl, or C1-4 acyl; and k′, l′, and m′ each independently represents an integer of 1 to 20.
In addition, in Patent document 2, multi-branched polymers which are obtained by copolymerizing a monomer mixture containing at least a monomer (A3) represented by the formula (2)

(in the formula, R111 to R113 each independently represents hydrogen or C1-4 alkyl; R114 represents hydrogen, C1-4 alkyl, or C1-4 acyl; and n′ represents an integer of 1 to 20) and monomer (A4) represented by the formula (3)

(in the formula, R115 to R117 each independently represents hydrogen or C1-4 alkyl; and R118 to R122 each independently represents hydrogen, halogen, C1-4 alkyl, or C1-4 haloalkyl with a proviso that at least one of R118 to R122 is C1-4 α-haloalkyl), and solid polymer electrolytes which use these multi-branched polymers are described.
Moreover, in Patent document 3, a block copolymer composition characterized by containing a block copolymer formed from a segment (A5) which contains 10 to 100 mol % of at least one polar monomer selected from the group consisting of the following polar monomers 1, 2, and 3 as a constituent, segment (A6) which contains less than 10 mol % of the same polar monomer as a constituent, and ester compound; and a solid polymer electrolyte which uses the composition are described.
Polar monomer 1: a polar monomer having at least one polymerizable unsaturated bond and at least one functional group selected from the group consisting of hydroxyl, nitrile, carboxyl, amino, and amido.
Polar monomer 2: a polar monomer represented by the formula (4)CH2═CR201—COO—(CH2—CHR202—O)t—R203  (4)
(in the formula, R201 to R202 each independently represents hydrogen or C1-5 alkyl; R203 represents C1-5 alkyl or phenyl; and t represents an integer of 1 to 25).
Polar monomer 3: a polar monomer represented by the formula (5)CH2═CR204—COO—(CfH2f—COO)g—R205  (5)
(in the formula, R204 represents C1-5 alkyl; R205 represents C1-10 alkyl or phenyl; and f and g each independently represents an integer of 1 to 20).
However, none of the solid polymer electrolytes described in the abovementioned Patent documents had thermal characteristics, physical characteristics, and ionic conductivity which were satisfactory.
On the other hand, as a joining method of cell separators, a method to join by a porous adhesive-resin layer formed from polyfluorovinylidene is described in Patent document 4. In this document, it is disclosed that the adhesive resin used turns into a porous film without being dissolved in an electrolyte and that the ionic conductivity can be adjusted by changing porosity and film thickness.
Additionally, in Patent document 5, a separator for adhesive composition-supporting cells is described as a cell/separator joined body where cells and separators are joined. In this document, a method to make a porous substrate support a heat-crosslinkable adhesive composition formed from polyfunctional isocyanate and reactive polymer is disclosed.
However, with such joining methods using adhesives, it was difficult to maintain adhesive strength when cells are used and the necessity to impart electrolyte properties to the heat-crosslinkable adhesives having no ionic conductivity by introducing a nitrile compound and acrylic-modified fluororesin was a problem.    [Patent document 1] Japanese Laid-Open Patent Application No. 2002-216845    [Patent document 2] Japanese Laid-Open Patent Application No. 2001-181352    [Patent document 3] Japanese Unexamined Patent Application, First Publication No. Hei 11-240998    [Patent document 4] Japanese Unexamined Patent Application, First Publication No. Hei 10-172606    [Patent document 5] Japanese Laid-Open Patent Application No. 2004-47439